Jared Harris of Mad Men Is Engaged

The former Mad Men star, 51, is engaged to his longtime girlfriend, Allegra Riggio, 38.

Riggio couldn't hold back her excitement on social media, posting a Vine of her heart-shaped Erica Courtney sparkler and Tweeting up a storm about the engagement, which was first confirmed by an E! News source.

"SOOOOOOOO HAAAAAAAPPYYYYYYYY AAAAAAAA!" the brunette beauty wrote to one of her followers.

In response to another follower who congratulated the pair, Riggio wrote, "THANK YOU!!!! We're giddy and adorable. <3"

As for the diamond itself, according to a release sent out by the jeweler, the heart-shaped diamond rose gold engagement ring was custom designed. It features an "H" initial on the gallery, and also has diamonds placed around the band.